BECKLEY, W.Va. -- A team of independent investigators has concluded that a corporate culture at Massey Energy put coal production before safety, prompting a collection of major safety infractions that caused the Upper Big Branch Mine Disaster.

The investigators, led by longtime safety advocate Davitt McAteer, found that Massey's pattern of longstanding and widespread violations, persistent intimidation of workers, and constant battling with regulators "can only be accepted where the deviant has become normal."

McAteer said his team found that Massey ignored well-understood practices -- such as proper ventilation, cleaning up explosive coal dust and maintaining mining equipment -- that can prevent all coal-mine explosions.

"The company ran this mine in a profoundly reckless manner," McAteer said during a closed-door briefing with families of the 29 miners who died in the April 5, 2010, explosion, according to several people who attended.

McAteer and his team focused most of their criticism on Richmond, Va.-based Massey, but also said state and federal regulators are to blame for not conducting adequate inspections or taking tougher enforcement actions to clean up the Upper Big Branch operation.

"The disaster at the Upper Big Branch Mine is proof positive that the [federal Mine Safety and Health Administration] failed its duty as the watchdog for coal miners," concluded the 126-page report from McAteer's team, formally known as the Governor's Independent Investigation Panel.

The report, commissioned last year by then-Gov. Joe Manchin, repeats some evidence and confirms some theories already made public, in many places citing stories about Upper Big Branch published by the Gazette.

But the report also outlines previously undisclosed oversights by government inspectors and detailed testimony that indicates a key Massey foreman did not perform required mine safety tests the day of the explosion -- and that such behavior by mine management may have been much more widespread.

It also cites autopsy reports that indicated that three-quarters of the Upper Big Branch victims had black lung disease. While unrelated to the disaster, McAteer said, "That is a terrifying number, an astonishing number" that needs further investigation.

Nationally, about 3.2 percent of underground coal miners have black lung. In West Virginia, the rate is 7.6 percent.

The McAteer team's report reveals for the first time two important findings that could explain how the mine's ventilation system failed to prevent explosive levels of methane from accumulating.

First, miners working the day of the blast reported that the flow of fresh air underground was reversed that morning and into the early afternoon, just before the explosion occurred at about 3:01 p.m.

Proper ventilation sweeps methane and coal dust out of the mine. Air going the wrong way could have helped set the stage for the disaster.

Second, investigators learned that pumps deep inside the mine had broken over the Easter weekend before the Monday explosion, allowing water to accumulate in a manner that would block proper airflow through underground tunnels.

McAteer's team concluded that the blast erupted when the longwall machine's shearer cut into a piece of sandstone. The resulting spark, the team believes, ignited a pocket of methane that seeped onto the longwall face from the mined-out area, or gob, behind the mining machine.

Water sprays on the longwall cutting shearer had been disabled or were clogged, meaning the flow was insufficient to extinguish the ignition before it turned into a major explosion.

Making matters worse, McAteer's team found, illegal levels of coal dust that had not been cleaned up provided fuel that sent the blast ricocheting in multiple directions throughout more than two miles of underground tunnels.

"A great deal went wrong and a great many problems occurred that led to this disaster," McAteer said during a press conference. "The most profound of these problems is that the most basic and fundamental safety practices were neglected and were not followed."

In a prepared statement, Massey general counsel Shane Harvey repeated the company's argument that the explosion involved a "massive inundation of methane-rich natural gas" that the company could not anticipate or control.

"Our experts feel confident that coal dust did not play an important role," Harvey said. "Our experts continue to study the UBB explosion and our goal is to find answers and technologies that ultimately make mining safer."

But McAteer's report contains an entire chapter, called "The Footprint of a Disaster," that details the physical evidence supporting the conclusion that coal dust fueled the explosion's rush into far corners of the mine.

Joe Main, assistant labor secretary in charge of MSHA, welcomed parts of McAteer's report that support his agency's version of what happened at Upper Big Branch. And, Main said, his agency has learned lessons from the disaster.

"Could we have done more? The answer is yes," Main said. "And have we done more? The answer is yes. We're using tools that weren't in use on April 4."

McAteer's report revealed that Gerald Pauley, the state's main inspector assigned to Upper Big Branch, did not always complete his inspections of the site and had not examined the crucial longwall section since Dec. 15, 2009.

Senate President Earl Ray Tomblin, acting as governor, said the state Office of Miners Health, Safety and Training has already shifted resources to give inspectors more time for larger mines like Upper Big Branch.

"Our inspectors are now working more frequently on weekends, allowing for inspections, as the report suggests, at any hour and on any day," Tomblin said in a statement.

Manchin said that McAteer's report makes clear that "this tragedy could have been prevented and these types of mistakes should never be repeated."

The report recounts Massey's long-troubled history of mine safety and environmental disasters, and concludes the company has "an inadequate commitment to safety ... coupled with a window dressing safety program."

"The story of Upper Big Branch is a cautionary tale of hubris," the report says. "A company that was a towering presence in the Appalachian coalfields operated its mine in a profoundly reckless manner, and 29 miners paid with their lives for the corporate risk-taking."

The report notes that Massey's vice president for operations, Chris Adkins, is scheduled to become co-director of Alpha Natural Resources' main safety program after Alpha completes its acquisition of Massey next month.

McAteer said he's concerned that Alpha executives "have not grasped the magnitude of the problem" with Massey's safety culture and practices. "Those questions need to be answered by the purchasing company," he said.

The report proposes a long list of reforms, including more resources for regulatory agencies, tougher enforcement of existing safety standards, and beefing up of those rules with new legislation.

McAteer urges the coal industry to put as many resources into improving mine safety technology as it has into mine production advances and says lawmakers should make corporate officials more accountable for safety violations.

And, the report calls for an overhaul of the way serious mining accidents are investigated in the first place, allowing for a more public and transparent process.

McAteer's team also blames the disaster in part on the coal industry's longstanding influence on West Virginia politics.

"The reality that powerful industries and their leaders cast long shadows over the state's government is not unique to West Virginia, nor is it unique to the coal industry," the report says. "It is a problem facing regulators of any large industry.

"But, with a powerful national lobby, the coal industry poses unique challenges for small state agencies that try to regulate it with inadequate resources," the report says. "For those dedicated safety officials and for the workers whose lives hang in the balance, the politics of coal must be acknowledged in any discussion of workplace safety and a commitment must be made to ensure that the public interest -- miners' safety -- is the foremost consideration."

McAteer's team is the first to complete its investigation into the worst U.S. coal-mining disaster in nearly 40 years. Separate federal and state probes aren't expected to wrap up until late this year at the earliest. Although Upper Big Branch was a non-union mine, the United Mine Workers also plans a report on the disaster.

A federal criminal probe is also ongoing. So far, only two low-level Massey employees have been charged.